A number of systems for supporting pipes and other components from elongated, U-section components variously termed struts and channels have heretofore been proposed. Systems of the foregoing character of which we are aware are disclosed in U.S. Pat. Nos.: 1,668,953 issued May 8, 1928, to Erickson for MOLDING FOR ELECTRIC CABLES; U.S. Pat. No. 2,273,571 issued Feb. 17, 1942, to Hafemeister for PIPE HANGER; 3,042,352 issued Jul. 3, 1962, to Stamper for PIPE HANGER; U.S. Pat. No. 3,132,831 issued May 12, 1964, to Stamper for CLIP-ON PIPE HANGER; U.S. Pat. No. 3,226,069 issued Dec. 28, 1965 to Clarke for HANGER FOR CYLINDRICAL CONDUITS AND THE LIKE; 3,527,432 issued Sept. 8, 1970, to Lytle for PIPE OR TUBING SUPPORT; U.S. Pat. No. 3,565,385 issued Feb. 23, 1971, to Zurawski for FLUORESCENT TUBE BOX SUSPENSION SYSTEM AND MEANS; U.S. Pat. No. 3,650,499 issued Mar. 21, 1972, to Biggane for CLAMP FOR PIPE SUPPORT WITH SLANTING PIVOTAL ASSEMBLY; U.S. Pat. No. 4,417,711 issued Nov. 29, 1983, to Madej for PIPE HANGER; and U.S. Pat. No. 4,695,019 issued Sept. 22, 1987, to Lindberg et al. for NON-METALLIC STRUT SYSTEM and in: Offenlegungsschrift No. 2164991 filed 28 Dec. 1971 by Niedax Ges. F. Verlegungsmaterial mbH and laid open to public inspection on 12 July 1973 and a Spring 1987 catalog from Aickinstrut, Inc., P. 0. Box 569, Redmond, Washington 98073.
Systems of the type disclosed in the foregoing patents and the Aickinstrut catalog with surface mounted struts or channels have been in use for over fifty years to support pipes, electrical raceways, and other system components from the floors, walls, and ceilings of buildings and from other structures. The struts or channels of the system are attached to the structure; and clamps, connectors, and other fittings are employed to attach the supported component (or load) to the channels or struts.
The earlier systems of this type were fabricated from such then available materials as cold rolled steel (see, for example, above-cited U.S. Pat. Nos. 1,668,953 and 2,273,571), and a number of systems of comparable character have been proposed in more recent years (see above cited U.S. Pat. Nos. 3,042,352; 3,132,831; 3,226,069; 3,565,385; 3,650,499; and 4,417,711). These heretofore proposed systems have the decided disadvantage that they offer little resistance to corrosion unless painted or galvanized. Even then, they deteriorate rapidly in aggressive chemical environments, for example in pulp mills and in buildings housing plating tanks. Therefore, as engineered polymers became available, a number of manufacturers substituted those materials for the theretofore employed steels and other metals. To date, this has met with only limited success. This is primarily because the designers of non-metallic support systems have not taken into account the physical differences between the non-metallic and metallic materials they employed. 0f particular significance in this respect are the typically quite different coefficients of friction of the metallic and non-metallic materials employed in systems of the type under discussion.
Specifically, in a typical, heretofore proposed system with metal components, there is a simple frictional fit between the supporting strut or channel and the fixture installed in that channel to support a from it (see, for example, above cited U.S. Pat. Nos. 3,226,069; 3,527,432; 3,565,385; 3,650,499; and 4,417,711) With non-metallic, engineered polymers substituted for the theretofore utilized metallic components (see, as an example, above-cited U.S. Pat. No. 4,695,019), this approach proves somewhat less than satisfactory. Due to the much lower coefficients of friction, the load-supporting fixture can easily slip along the supporting strut or channel when a polymer is substituted for metal in a conventional support system design, allowing the load to shift. This is especially true in applications in which the supporting channels are vertically oriented, particularly if the load is relatively heavy or subjected to vibration or hammering and because the pipe runs are often then employed as ladder rungs. Shifting loads are of course very undesirable as they radically increase the potential for system failure.
The use of stop blocks in the load-supporting channel or a complicated channel and fixture arrangement with extended continuous contact therebetween (see the above-cited U.S. Pat. No. 4,695,019 and the Aickinstrut catalog) to increase the fixture-to-channel contact area and therefore increase the friction between these system components and minimize slippage of the supported load has heretofore been proposed. This approach is, however, not without its disadvantages. Perhaps the most important of these is that the average installer must be reeducated and his resistance to employing a non-conventional system with an additional component overcome. Secondly, available stop blocks are relatively expensive; and large numbers of these components (typically four per foot) are required. Therefore, in a typical installation, systems employing stop blocks are not competitive unless corrosion problems are severe and support systems with metallic components can not be employed. Finally, and as a corollary, systems with stop blocks are typically not competitive because of the additional labor required to install a system of that character.
Another approach to preventing slippage that is suggested in the prior art is to notch the side walls of the U-sectioned supporting channel and to install the load connecting system components in these notches so that the fitting cannot slip relative to the channel, even if the latter is vertically oriented. The above-cited Stamper U.S. Pat. Nos. 3,042,352 and 3,132,831 disclose systems of the just-described character. Again, however, the heretofore proposed system is not one which would be satisfactory if channels fabricated of engineered polymers rather than metal components were employed to get the corrosion resistance and other benefits of those non-metallic materials. Specifically, the slots or notches in the Stamper channels leave lips or ears of very small section on which the supported load is imposed. In applications involving heavy loads or vibration, these lips would be very apt to fail, resulting in system failure. If an engineered polymer with its lower shear strength were substituted for steel in Stamper's systems, this tendency would be many times aggravated; and the substitution would produce a system of little if any value.
Furthermore, failure of one load will often have a domino effect with adjacent loads failing until the entire system or a large section of it has been destroyed. Thus, the heretofore proposed support systems have the important drawback that they are unable to prevent such catastrophic failures.
Another salient disadvantage of the Stamper systems is that it would be extremely difficult, if possible at all.TM.to connect cross channels between parallel horizontal or vertical runs. The side walls of the Stamper systems are so thin, in this respect, that it would not be practical to support a cross-channel of the Stamper type from the side walls of a normally extending channel as would be required to connect those channels together. Thus, as a grid of supporting channels is typically required, the applications in which the Stamper systems would be useful are extremely limited.
Still another disadvantage of the Stamper systems is that no provision is made for retaining a channel nut or other fixture component in the load-supporting strut. This is a significant drawback as channel nuts and the like can be employed to advantage in attaching connectors and other fittings via which one channel may be connected to a cross channel and also via which a variety of different load devices may be attached to a channel. Modifications of the Stamper channels which would allow the use of channel nuts and the like would be impractical because the channel configurations required to retain such devices would increase the cost of the channels to the point where the system would become economically non-competitive if the channels were rendered in metal.
Niedax discloses a support system which is like those of Stamper to the extent that it employs notched channels. These notches are formed in the rearmost, free or exposed edges of cooperating flanges which are integral with, and spaced inwardly from, the side walls of the channels. The channels are fabricated from thin, non-load bearing sheet metal. Material of that character is employed so that the notches can be stamped out and so that the channel can be fabricated by bending at a low enough cost to make it practical. In the Niedax system, the channels are notched only so that the associated, load-attaching components can be inserted into the channels once the latter have been embedded in concrete. The channels are not intended to be surface mounted. They would sag and collapse, and/or the load would pull on the channel and cause its side walls to fail unless the channel were embedded. In short, the Niedax channel is not a structural member or support. It is instead intended to, and does, function only as an anchor as is made clear by the title of the reference -- Anchor Rail.
To at least a large extent, the foregoing and other disadvantages of the just-discussed support systems are eliminated in those support systems disclosed in parent U.S. Pat. application Ser. No. 252,855. These novel, improved support systems, generally speaking, include elongated struts or channels which can be surface mounted and clamps, connectors, and other fittings for attaching a load to the supporting channel. The system components may be fabricated of non-metallic materials. This makes the novel systems disclosed in the U.S. Pat. application Ser. No. '855 application appropriate for even highly corrosive environments. At the same time, the system components are simple and relatively inexpensive to manufacture; and the resulting systems are accordingly sufficiently inexpensive to be employed in even the most mundane of applications.
Perhaps most prominent among the novel features of the systems disclosed in the '855 application is the type of supporting channel which is employed. Like conventional channels, they have a U-shaped cross-section; and, like those disclosed in Stamper U.S. Pat. Nos. 3,042,352 and 3,132,831, the channels disclosed in the '855 application have notches in which the load-supporting fittings can be engaged to keep the load from shifting, even in demanding applications in which the channels are vertically oriented and the loads are heavy or of a nature which causes hammering or vibration. In contrast to the Stamper channels, however, these notches are not formed in the side walls of the channel. Instead, they are molded or otherwise formed in the rearmost, free or exposed edges of cooperating flanges which are integral with, and spaced inwardly from, the side walls of the channels.
One consequence of this novel construction is that the load-supporting capacity of the channel is dramatically increased over that available in a Stamper-type channel even though the materials may have less shear strength because much thicker sections are practical. A second, also significant, advantage of the channels disclosed in the '855 application is that channel nuts and other trapped-type fittings can be employed, greatly increasing the versatility of the channel by increasing the types of fittings which may be employed with it. At the same time, and because they are fabricated from non-metallic materials, the channels disclosed in the '855 application can be supplied at competitive costs whereas they could not be, if fabricated from metal as Stamper's are.
The channels disclosed in the '855 application are fabricated from rigid, vibration absorbing, engineered polymers. And, even though applicant's materials may have less shear strength than Stamper's or Niedax's, much thicker sections are practical. One consequence of this novel construction is that the load-supporting capacity of the channel is dramatically increased over that available in the channel of the Stamper or Niedax systems. This makes it entirely feasible to use the channels disclosed in the '855 case in applications requiring surface mounting and relatively long, unsupported runs. For example, they can be end supported from the exposed surfaces of vertically or horizontally oriented and spaced apart beams. Again, this is an important application for which the Niedax channel is totally unsuitable. It must be embedded in a structural material such as concrete to be useful because of its inability to otherwise support a load of any appreciable magnitude.
A further, important difference between the Niedax channel and those disclosed in the '855 application is the channel configuration--rectangular as opposed to trapezoidal. One important advantage of the rectangularly configured channels disclosed in the '855 application is that such channels can easily be connected into a network or grid of intersecting channels. It would be difficult and expensive, if practical at all, to so connect Niedax-type channels because of their slanting side walls.
Yet another, also significant, difference between the channels disclosed in the '855 application and those of Niedax is that the channels disclosed in the '855 application are fabricated of vibration absorbing or damping polymers. Niedax does not make channels of this or any comparable material. Instead, his channels are made of a vibration transmitting material; and the embedding of the channel in concrete is relied on for vibration damping.
Furthermore, the channels disclosed in the '855 application have segments with different thicknesses. This permits the several segments to be designed in a manner which optimizes the structural attributes of the channel. The only practical way to fabricate the Stamper, Niedax, and other metal channels is to bend them from sheet metal; and this technique could of course not be employed to fabricate a multisegment-multithickness strut.